[PATCH 0/1][SRU][B][C][D][OEM-B]PC SN720 NVMe WDC 256GB consumes more power in S2Idle than during long idle

[AceLan Kao]

To avoid conflicts, this patch assumes below commits have been applied
on top of master-next branch on Bionic, Cosmic, and Disco kernel,
since both patches modify the same files on the same position for the
same issue.
https://lists.ubuntu.com/archives/kernel-team/2018-November/096832.html

BugLink: https://bugs.launchpad.net/bugs/1805775

[Impact]
On new systems that facilitate s2idle, we observed the power consumption
raises higher than long idle does during s2idle with Western Digital PC
SN720 NVMe SSD SDAPNTW-256G.

Short idle: 5.3
Long idle: 3.0
S2I: 5.07

[Fix]
Windows doesn't put nvme to D3 in modern standby, and uses its own APST
feature to do the power management. To leverage its APST feature during
s2idle, we can't disable nvme device while suspending, too.
So, here is what we did on the driver, 1. prevent nvme from entering D3,
2. prevent nvme from being disabled when suspending.

[Test]
Verified on the WD NVMe, it fixes the power consumption issue with no
regression. And the power consumption decreases to 1.66W during s2idle.

[Regression Potential]
Low, the patches only applied to specific nvme module, and from our test,
the system is still stable.

AceLan Kao (1):
  SAUCE: pci/nvme: prevent WDC PC SN720 NVMe from entering D3 and being
    disabled

 drivers/nvme/host/pci.c | 2 ++
 drivers/pci/quirks.c    | 1 +
 2 files changed, 3 insertions(+)

-- 
2.17.1